Three-Way Systems Do Not Exist

We argue that argument encoding systems that seem to involve three syntactic core cases (nominative/absolutive, ergative, accusative) are actually common ergative or accusative systems syntactically, with overt case markers for each of the two cases that disappear in intransitive contexts. Based on evidence from Kham, Djapu, Nez Perce, Upriver Halkomelem, Dyirbal, and Pitjantjatjara, we show that a purely morphological approach to differential marking in terms of scale-driven optimization via harmonic alignment and local conjunction (based on Aissen (2003)) can derive these systems straightforwardly if a transitivity scale is postulated in addition to the standard definiteness, animacy, and person scales (Hale (1972), Silverstein (1976)). Since apparent three-way systems usually also involve differential marking sensitive to Hale/Silverstein scales, a conservative extension to (in)transitivity suggests itself. In the final part of the paper, we show that the new morphological approach is either directly supported by, or at least compatible with, the available syntactic evidence.